You drop a 1.70 kg book to a friend who stands on the ground atdistance D = 12.0 m below. If your friend's outstretched hands areat distance d = 1.60 m above the ground (see the figure), (a) howmuch work Wg does the gravitational force do on the book as itdrops to her hands? (b) What is the change ΔU in the gravitationalpotential energy of the book-Earth system during the drop? If thegravitational potential energy U of that system is taken to be zeroat ground level, what is U (c) when the book is released and (d)when it reaches her hands? Now take U to be 100 J at ground leveland again find (e) Wg, (f ) ΔU, (g) U at the release point, and (h)U at her hand
